1. Field of the Invention
The present invention relates to an air core filling system for furniture, especially for a mattresses and seating furniture, but also for car seats and camping furniture which have an air-filled core.
2. The Prior Art
Reclining or seating furniture with an air-filled core have long been known. They are regarded as the logical further development of the waterbed, which was originally preferably used in hospitals. As a result of the water filling of the mattress, it was possible to achieve a more even pressure distribution over the entire contact surface in order to prevent the feared bedsores.
Waterbeds come with a number of disadvantages, however. Bodily weak persons have difficulties changing their lying position. This is caused by the fact that in the case of a change of position, it is necessary that the water in the mattress under the body needs to be moved too. Such mattresses are therefore even dangerous for babies. Further disadvantages are the comparatively cumbersome handling and the very high weight. A further problematic aspect is that it has been noticed that water is a very good heat-transfer medium. The filling with water, which normally has room temperature at most, needs to be heated continually to a temperature of approximately 25° C. to 28° C. in order to avoid withdrawing temperature from the body in an unpleasant and especially hazardous manner. Such temperatures are absolutely damaging for persons with venous diseases. Since air is an adverse heat-transfer medium, tempering devices can be omitted in mattresses with an air core without having to give up the known advantages of the waterbeds. All other indicated disadvantages of waterbed can be avoided by using a mattress with an air core. Moreover, there is a better adjustment of the support to the user's body shape because there is no lateral displacement of water as in the waterbed. Instead, the displaced air quantity will lead to an even increase in the air pressure over the entire volume.
The disadvantageous aspect in seating furniture or mattresses with an air core is however that they are not absolutely gas-tight. As a result of gas diffusion, especially in the case of pressure loads during use, there will be a loss of pressure in the air core which requires periodic refilling. Older systems comprise filling systems which are driven manually or by means of an electromotor in order to hold the once chosen degree of hardness over a substantially indefinite period of time.
An air-core filling system is known from U.S. Pat. No. 4,306,322, comprising an integrated hinged pump which is connected directly with the air core via a ball check valve. The pump is flipped out for re-filling the air core and is compressed manually. It may occur relatively easily that the air core is overfilled and becomes too hard, so that air needs to be bled via a further valve. This cumbersome operation was soon replaced by systems in which air can be filled only up to a preset pressure by means of a control valve.
Automatic refilling systems were also developed in order to also enable a continuous maintenance of the desired pressure in the air core. EP 0 620 716 B1 describes an upper mattress with an integrated air system for example in which a circumferential foamed-material frame is present about an air core in which an air reservoir and supply system is integrated. It consists of an air pump, an air reservoir and a pressure regulating valve. When the foamed-material frame is loaded when the user lays down on the mattress, a pressure is exerted on the pump body integrated in the foamed-material frame which conveys the air from said pump bodies to an air reservoir. The air coming from the pump bodies is compressed and stored there. A one-way valve is installed in the connecting line between the pump bodies and the reservoir. Once the mattress is relieved, the pressure from the pressure reservoir balances the pressure in the air core of the mattress up to a value again which is set on the pressure regulating valve. Once the boundary zone is relieved, the pump bodies suck in ambient air through a further valve by returning to their initial position.
This system has a number of disadvantages however. The air from the pump bodies will only be pressed into the reservoir when the pressure on the boundary zone by sitting on the same is sufficiently high, which means in other words when the user sits fully on the boundary zone. Sitting down usually occurs in such a way that the boundary zone is loaded only by the leg but not by the buttocks. The consequence is insufficient compression of the pump bodies.
A further disadvantage is that the reservoir always needs to be under pressure in order to keep the air core of the mattress at the set value. If there is a loss of pressure in the reservoir for any reason, e.g. by introduction of dust into the one-way valve to the reservoir, maintaining the set pressure value will no longer be possible. On the other hand, the built-up pressure of the compressed air can only be reduced via the air core. This leads to the consequence that a pressure of 100 mbar and more can build up in the reservoir under intensive use, as a result of which the connections and valves are subjected to a high load. A further disadvantageous aspect are the considerably long distances from the air entrance to the reservoir and further to the pressure regulating valve, thus leading to large surface areas for gas diffusion. The likelihood of leakages also rises as a result of the numerous connection points. A further disadvantageous aspect is that an intended pressure reduction in the air core is only possible by diffusion loss, which is why it takes a long time until the pressure in the air core has settled to a lower level.
The present invention is therefore based on the object of avoiding these disadvantages in such a way that a pump and control system is created which works without a reservoir and in the entire air core filling system has the same pressure as in the air core when not loaded. The air supply system in accordance with the invention further has a substantially smaller overall size with considerably reduced connecting lines and also has a number of connecting points which is lower in comparison with the system according to EP 0 620 716 B1 in order to thus reduce any hazards by unintended pressure loss.
The invention will be explained in greater detail by reference to the attached drawing.